Critical dimension control by use of a photo agent

ABSTRACT

A method for critical dimension control in which a substrate is received having an underlying layer and a patterned layer formed on the underlying layer, the patterned layer including radiation-sensitive material and a pattern of varying elevation with a first critical dimension. The method further includes applying an overcoat layer over the patterned layer, the overcoat layer containing a photo agent selected from a photosensitizer generator compound, a photosensitizer compound, a photoacid generator compound, a photoactive agent, an acid-containing compound, or a combination of two or more thereof. The overcoat layer is then exposed to electromagnetic radiation, wherein the dose of electromagnetic radiation applied to different regions of the substrate is varied, and then the overcoat layer and patterned layer are heated. The method further includes developing the overcoat layer and the patterned layer to alter the first critical dimension of the patterned layer to a second critical dimension.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/335,991, filed on May 13, 2016, entitled “CriticalDimension Control by Use of a Photo-Active Agent,” which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to location-specific critical dimension (CD)alteration/correction flows and processes for improvement of CDuniformity.

Description of Related Art

Techniques disclosed herein relate to microfabrication and, inparticular, relate to photolithography and patterning processes. Inmaterial processing methodologies (such as photolithography), creatingpatterned layers typically involves the application of a thin layer ofradiation-sensitive material, such as photoresist, to a surface of asubstrate. This radiation-sensitive material is transformed into apatterned mask that can be used to etch or transfer a pattern into anunderlying layer on a substrate. Patterning of the radiation-sensitivematerial generally involves exposure by a radiation source through areticle (and associated optics) onto the radiation-sensitive materialusing, for example, a photolithography system. This exposure creates alatent image or pattern within the radiation sensitive material whichcan then be developed. Particular wavelengths of light cause exposedportions of the radiation-sensitive material to change its solubility byeither becoming soluble or insoluble to a particular solvent. Developingrefers to dissolving and removing a portion of the radiation-sensitivematerial to yield a topographic or physical pattern, that is, a reliefpattern. For example, developing can include removal of irradiatedregions of the radiation-sensitive material (as in the case of positivephotoresist), or non-irradiated regions (as in the case of negativeresist) using a developing solvent. The relief pattern can then functionas a mask layer for subsequent processing.

As industry shrinks continue to push minimum feature sizes to smallerand smaller CDs and with the delay and potential high cost of EUV (13.5nm), the industry has looked for processes that further extend theircurrent ArF (193 nm) immersion (ArFi) scanner systems, including bothinfrastructure and expertise. CD alteration, such as shrinking/slimming,of the traditional post photolithography ArFi near resolution-limitedresist features is one such extension. The ability to improveacross-wafer critical dimension uniformity (CDU) around a current CDtarget, and/or to alter the CD of holes, trenches and/or lines in acontrolled process has current and future applications in singlepatterning, such as in logic design where gate layers have very smallfeatures on a slightly less aggressive pitch, and in doublepatterning/multi-patterning schemes, such as in Litho-Etch-Litho-Etch(LELE) or Litho-Etch repeated “n” times (LE^(n)), Litho-Litho-Etch(LLE),and precursors for sidewall spacers.

The CD alteration process has historically been achieved by 3 methods.The first CD alteration method uses a post-photolithography etch-basedplasma trim process for lines (or tapered etch process of holes ortrenches), where the process flow includes Coat→Expose→Post ExposureBake (PEB)→Develop (nominal temperature)→Etch Trim/Shrink. Morerecently, a second CD alteration method, which is a wet-process, hasbeen proposed in which additional processing steps are performed in thelitho-cell, such as a positive tone hot develop (>30° C.) process or anacid rinse/acid rinse bake process, or a combination of the two. The hotdevelop process shifts the de-protection level at which developmentstops to a lower level of de-protection. The positive tone hot developprocess flow includes Coat→Expose→PEB→Positive Tone Develop (nominaltemperature)→Positive Tone Hot Develop (>30° C.). The acid rinse/acidrinse bake process shifts the de-protection level within the matrix ofthe first developed feature to a higher level, allowing for a seconddevelop process to alter the CD of the feature using standard ormodified develop solution. The acid rinse/acid rinse bake process flowincludes Coat→Expose→PEB→Positive Tone Develop (nominaltemperature)→Acid Rinse→Acid Rinse Bake→Positive Tone Develop (nominaltemperature). The combination process flow includesCoat→Expose→PEB→Positive Tone Develop (nominal temperature)→PositiveTone Hot Develop (>30° C.)→Acid Rinse→Acid Rinse Bake→Positive ToneDevelop (nominal temperature). Even more recently, a third CD alterationmethod, which is also a wet-process, has been proposed in whichadditional processing steps, such as a non-location-specific floodexposure and bake prior to a second development, are utilized to bringthe film to a fully or nearly fully de-protected state, at which pointdevelopment is controlled by development time. The process flow includesCoat→Expose→PEB→Positive Tone Develop (nominal temperature)→FloodExpose→Flood Bake→2nd Develop.

The wet-process examples above are a subset of the various ways in whichwet-process CD alteration has been proposed historically.

The first CD alteration method, which is an etch-based plasma method,has the benefit of less potential for pattern collapse due to the lackof any surface tension effects (that are present in wet processing),which means no capillary forces, but has shown the following possibleissues that become more problematic at very small CD targets andcontinued shrinking: the potential to negatively impact or damageorganic bottom anti-reflective coatings (BARCs); some secondary effectssuch as polymer densification that begin to negatively impact structuralintegrity performance at very small dimensions; pattern density effects,i.e., iso-dense bias; chamber etch uniformity concerns (center-to-edge);process stability/maintainability (due to re-deposition on chamberwalls); and/or potential high additional front-end capital cost.

The recently proposed second CD alteration method, which is a wetprocess, while avoiding etch-specific issues, has the problem of havingthe magnitude and control of CD change highly correlated to aerial imagelog-slope (ILS) and resulting de-protection matrix/gradient in the caseof the positive tone hot develop process flow.

The other process flows of the second CD alteration method (e.g., theacid rinse/acid rinse bake or the combination process flow), whichinclude the acid rinse and bake steps, similarly come with some newconcerns. It is ultimately a diffusion-based process, meaning localamount of CD alteration is correlated to local concentration levels andreaction kinetics as well as time and temperature. Via simulation, ithas been observed that this can lead to a potential undercutting due tolocal changes in the de-protection matrix through defocus and possibly apattern breaking failure mechanism due to non-homogeneity of resistcomponents leading to stochastic weak points in the line.

The third CD alteration method, which is also a wet process, where theprocess flow includes the blanket flood exposure and flood bake,similarly comes with some new concerns. Because it attempts to take thefilm to a fully de-protected state (for homogeneity benefits), itrequires modified develop solution conditions to ensure process controlvia develop time.

Historically, wet CD alteration-based concepts revolved around methodsin which the time and/or concentration of a wet chemistry developmentwas linked with the amount and control of CD alteration. Furthermore, tomaintain profile control while maximizing the CD alteration amountachievable under these additional development processing steps (CDalteration amount previously limited by level of de-protection remainingwithin the resist matrix from the patterning exposure), the resistmatrix was attempted to be taken to a more homogenized state byintroducing methods to increase the de-protection level, if not fullyde-protect the resist matrix, e.g., by blanket flood, thermal acidgenerators (TAGs), and acid rinses.

The condition of a fully de-protected resist matrix prior to theslimming/shrinking develop step (i.e., at the 2nd develop) generallymeant that top-loss would be equivalent to side loss. Furthermore, itmeant that the develop chemistry had to be altered, for example, using anegative tone develop (NTD) process and developing at the develop rateminimum (R_(min)), using a dilute aqueous base developer in a positivetone develop (PTD) process and developing at a modified develop ratemaximum (Rmax), using an inhibited aqueous base developer in a PTDprocess and developing at an inhibited Rmax, and/or using a cold aqueousbase developer in a PTD process and developing at a modified R_(max), tomake the CD alteration rate reasonable (e.g., 0.1 to a few nm/s) withoutcompletely washing away a feature in the first few milliseconds of the2nd develop. Similarly, the de-protection matrix pre-slimming developcondition (2nd develop) left by acid rinse diffusion and bake generallymeant that top-loss would be equivalent to side loss.

There is thus a need for a method to maximize the amount of CDalteration achievable while allowing for more standard developmentconditions.

SUMMARY OF THE INVENTION

This disclosure offers an alternative way to maximize the amount of CDalteration and an alternative flow for control/correction. In anembodiment, the method comprises receiving a substrate having anunderlying layer and a patterned layer formed on the underlying layer,the patterned layer comprising radiation-sensitive material and furthercomprising a pattern of varying elevation and having a first criticaldimension. The method further comprises applying an overcoat layer overthe patterned layer, the overcoat layer comprising a photo agentselected from a photosensitizer generator compound, a photosensitizercompound, a photoacid generator compound, a photoactive agent, anacid-containing compound, or a combination of two or more thereof. Theovercoat layer is then exposed to electromagnetic radiation, wherein thedose of electromagnetic radiation applied to different regions of thesubstrate is varied, and then the overcoat layer and patterned layer areheated. The method further comprises developing the overcoat layer andthe patterned layer to alter the first critical dimension of thepatterned layer to a second critical dimension.

In another embodiment, the method comprises receiving a substrate havingan underlying layer and a radiation-sensitive material layer depositedon the underlying layer. The method further comprises exposing a firstwavelength of light through a patterned mask onto theradiation-sensitive material layer and performing a post-exposure bake;first developing the pattern-exposed radiation-sensitive material layerto form a patterned layer of varying elevation and having a firstcritical dimension; inspecting the patterned layer following the firstdeveloping; and applying an overcoat layer over the patterned layer, theovercoat layer comprising a photo agent selected from a photosensitizergenerator compound, a photosensitizer compound, a photoacid generatorcompound, a photoactive agent, an acid-containing compound, or acombination of two or more thereof. The overcoat layer is then exposedto electromagnetic radiation at a wavelength of 175 nm to 450 nm,wherein the dose of electromagnetic radiation applied to differentregions of the substrate is varied and is based on metrology dataobtained from inspecting the patterned layer following the firstdeveloping. The method further comprises performing a post-exposure bakeof the overcoat layer and patterned layer; and developing the overcoatlayer and the patterned layer to alter the first critical dimension ofthe patterned layer to a second critical dimension.

Of course, the order of discussion of the different steps as describedherein has been presented for clarity sake. In general, these steps canbe performed in any suitable order. Additionally, although each of thedifferent features, techniques, configurations, etc. herein may bediscussed in different places of this disclosure, it is intended thateach of the concepts can be executed independently of each other or incombination with each other. Accordingly, the present invention can beembodied and viewed in many different ways.

Note that this summary section does not specify every embodiment and/orincrementally novel aspect of the present disclosure or claimedinvention. Instead, this summary only provides a preliminary discussionof different embodiments and corresponding points of novelty overconventional techniques. For additional details and/or possibleperspectives of the invention and embodiments, the reader is directed tothe Detailed Description section and corresponding figures of thepresent disclosure as further discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will become readily apparent with reference to thefollowing detailed description, particularly when considered inconjunction with the accompanying drawings, in which:

FIGS. 1A-1C are schematic cross-sectional views of a slimming method inaccordance with an embodiment of the invention;

FIG. 2 is a table illustrating the various pathways to alter the radialdose signature delivered within-wafer to alter the final criticaldimension; and

FIG. 3 is a flow chart depicting a process flow for critical dimensionslimming according to an embodiment of the invention.

DETAILED DESCRIPTION

This disclosure offers an alternative method to maximize the amount ofCD alteration achievable, breaking from the de-protection matrix beingdictated by primary exposure conditions, and allowing for more standarddevelopment conditions. Furthermore, the method of this disclosureshifts CD alteration amount control to be largely controlled by flooddose rather than developer concentration and/or develop time, whichsimplifies the development process. Additionally, it introduces newphotoactive chemistries to be used as the primary mechanism for acidgeneration that will ultimately lead to better de-protection control ofthe feature. Finally, it uses location-specific critical dimension (CD)alteration/correction flows and processes for improvement of CDuniformity, and in some embodiments shifting of CD targeting as well,making use, in some embodiments, of after develop inspection (ADI)information in a feed forward (FF) process control scheme by means oflocalized dose control of a flood process step.

With this modified approach to CD alteration, within-wafer (WIW) controlschemes are also discussed.

The first embodiment of this invention proposes the use of an overcoatmaterial that coats over a critical dimension feature layer defined by atraditional photolithography flow. With specific reference to theschematic cross-sectional views of FIGS. 1A-1C, a substrate 10 comprisesan underlying layer 12 and a patterned layer 14 formed on the underlyinglayer 12. The patterned layer 14 comprises a radiation-sensitivematerial, for example a photoresist material, with a pattern of varyingelevation and a first critical dimension, CD1. An overcoat layer 16 isapplied over the patterned layer 14, as shown in FIG. 1A. The overcoatmaterial contains at least one photo agent, such as a photosensitizergenerator, a photosensitizer, a photoacid generator, a photoactiveagent, and/or an acidic compound, or any combination of two or morethereof.

Photosensitizer molecules can absorb light energy and transfer the lightenergy to another molecule, such as a photoacid generator (PAG). Thisenergy transfer can in turn activate the receiving molecule. In the caseof a PAG receiving the energy transfer, the PAG can then generate acid.Some photosensitizer compounds may transfer energy in a ground statewhile others may conduct the transfer in an excited state. Exemplaryphotosensitizer compounds include, but are not limited to, acetophenone,triphenylene, benzophenone, fluorenone, anthraquinone, phenanthrene, orderivatives thereof.

A photoacid generator (PAG) can be a cationic photoinitiator thatconverts absorbed light energy into chemical energy (e.g., an acidicreaction). The photoacid generation compound may include, but is notlimited to triphenylsulfonium triflate, triphenylsulfonium nonaflate,triphenylsulfonium perfluorooctylsulfonate, triarylsulfonium triflate,triarylsulfonium nonaflate, triarylsulfonium perfluorooctylsulfonate, atriphenylsulfonium salt, a triarylsulfonium salt, a triarylsulfoniumhexafluoroantimonate salt, N-hydroxynaphthalimide triflate,1,1-bis[p-chlorophenyl]-2,2,2-trichloroethane (DDT),1,1-bis[p-methoxyphenyl]-2,2,2-trichloroethane,1,2,5,6,9,10-hexabromocyclododecane, 1,10-dibromodecane,1,1-bis[p-chlorophenyl]2,2-dichloroethane,4,4-dichloro-2-(trichloromethyl)benzhydrol, 1,1-bis(chlorophenyl)2-2,2-trichloroethanol, hexachlorodimethylsulfone,2-chloro-6-(trichloromethyl)pyridine, or derivatives and/or combinationsthereof.

The photoactive agent can include a second PAG, a thermal acid generator(TAG), or a photo-destructive base, also known as a photo-decomposablebase. A photo-destructive base can include one or more base compoundsthat decompose in the exposed areas, which allows for a higher totalbase loading that can neutralize photoactive acids in the non-exposedareas. A photo-destructive base thus includes compounds that can providethis general base loading effect. The non-decomposed base will denatureone or more photo acids such that these photo acids are no longerphoto-sensitive, or no longer sensitive to radiation. As disclosedherein, by adding more base to a given resist film, a given acidconcentration can be reduced. Likewise, a given acid concentration canbe increased by selectively adding acid compounds.

Referring to FIG. 1B, the overcoat layer 16 is exposed toelectromagnetic radiation 20. The overcoat material upon exposure oflight, either directly or indirectly, produces acids, or changes acidconcentration, within the overcoat material. This exposure process canbe from any generic EM source, for example, a lamp, a laser, a bulb,etc. The EM source's exposure wavelength for generation of the acidwithin the overcoat material could be, but is not limited to, anywavelength, or range of wavelengths between 170-450 nm, which arewavelengths typical of photo agent material absorbance used by theindustry in photolithography, with exemplary wavelengths being at/around266 nm and/or at/around 365 nm. Depending on material properties, thewavelength and material choice for photo agents in the overcoat materialcould be chosen to escape the absorption of other components within thephotoresist matrix of the critical feature (e.g., for this situation, anexemplary choice of 365 nm wavelength as a target for materialabsorption and exposure). In other embodiments, the ratio of absorbanceof photo agents in the overcoat material compared to other componentswithin the photoresist matrix is significantly greater than 1 as toallow lower wavelengths to be chosen (e.g., for this situation, anexemplary choice of 266 nm wavelength as a target for materialabsorption and exposure).

According to an embodiment, the dose of electromagnetic radiationapplied to different regions of the wafer is varied. For example, thedose delivered to the wafer can be location specific to create localizedconcentrations of acid molecules in the overcoat material. Thelocation-specific dose can be controlled by several embodiment methods.In one method embodiment, use of digital pixel-based projection systemsis proposed. The system, an array of independently addressableprojection points, can project wafer level patterns that spatiallycharacterize critical dimension values of structures. The digitalpixel-based projection system can be embodied as a digital lightprocessing (DLP) chip, grating light valve (GLV), or other microprojection technology (“Other”), with a light source that can focus animage or pattern (optionally using a lens) onto a wafer and correct oradjust critical dimension means and non-uniformities. Location-specificdose control can be achieved in this system by light source power andsource shaping, projection mirror oscillation rate, and/or mirror “on”state to correct or adjust critical dimension means andnon-uniformities.

In another location-specific dose delivery method, a light source (anexemplary example being a 266nm laser beam) can be directed onto agalvo-controlled mirror system. The galvo-controlled mirror system(“galvo-mirror”) can re-direct the laser onto any location on the wafersurface allowing for wafer level patterns that spatially characterizecritical dimension values of structures. Location-specific dose controlcan be achieved in this system by laser pulse frequency, laser pulsepower, galvo mirror control (scan rates in 2-dimensions), and in someembodiments wafer control (substrate translation) to correct or adjustcritical dimension means and non-uniformities.

In another location-specific dose delivery method, dose is delivered viarotating and translating the wafer under a fixed light source. The lightsource, for example, could be a single controllable source (e.g., a300+mm size bulb) or a series of controllable, independent zones (e.g.,along the long axis of the light source). Similarly, the wafer could befixed, and the light could rotate and translate over the wafer. Such ahardware concept allows for many pathways to alter the dose signaturedelivered within-wafer (WIW) to alter the final WIW CD alterationsignature. For this embodiment, as shown in FIG. 2, the radial dosealteration can include variable settings for rotation, scan rate, powersetting, light source working distance, use of apertures, focalpositions, light source zonal control, to name a few, as well as anypermutations thereof. Thus, embodiments for exposing the overcoat layerto electromagnetic radiation can include scanning the wafer, scanningthe radiation source (e.g., a laser beam), rotating the wafer, or acombination of two or more thereof.

In another embodiment, exposure by any of the location-specific dosedelivery methods described above can be combined to correct or adjustfor critical dimension means and non-uniformities. Specific examples ofsub-process flows for the location-specific dose delivery methodinclude, but are not limited to:

Sub Flow A: XXX nm DLP or GLV or Other→Flood Bake

Sub Flow B: XXX nm Galvo-mirror→Flood Bake

Sub Flow C: XXX nm Rotation/Translation Flood→Flood Bake

Sub Flow D: XXX nm Galvo-mirror XXX nm Rotation/Translation Flood→FloodBake where XXX=175˜450 nm, for example 266 nm. Any other combination ofthe Sub Flows A-D may be used.

Referring again to FIGS. 1A-1C, following exposure of the overcoat layer16 to electromagnetic radiation 20, the overcoat layer 16 and patternedlayer 14 are heated or baked to drive acid diffusion from the overcoatmaterial into the radiation-sensitive material matrix (local diffusionprocesses will depend on local acid concentration in the near region)and ultimately de-protection of the protected polymer by the new acidincorporated into the radiation-sensitive material matrix. Then theovercoat layer 16 and patterned layer 14 are developed, for exampleusing positive tone developer as shown in FIG. 1C, to remove theovercoat layer and reduce the critical dimension of the patterned layer14 from CD1 to a second critical dimension, CD2. By way of example andnot limitation, the developer may be the traditional industry 0.26 NTMAH for positive tone develop or n-butyl acetate or cyclohexane, orsimilar negative tone solvents for negative tone develop.

With further regard to the processing flow using the overcoat materialto facilitate CD alteration, in accordance with one embodiment, and asshown in the flow chart 300 of FIG. 3, the process begins at 310 withinitial processing of the wafer (e.g., substrate 10 of FIG. 1A). At 320,a thin film is added, which may be referred to as the underlying layer(e.g., underlying layer 12 of FIG. 1A) into which a pattern is to betransferred. At 330, a coating of radiation-sensitive material, forexample a photoresist, is applied over the thin film. At 340, alithography process is performed on the radiation-sensitive materialcoating. More specifically, the radiation-sensitive material coating isexposed through a mask to a wavelength (λ) of light, typically in the UVspectrum, to create a patterned exposure. At 350, a first post-exposurebake (PEB #1) is performed. In 360, the pattern-exposedradiation-sensitive material coating is subjected to a first developmentprocess (1^(ST) DEV) to form a patterned layer, such as patterned layer14 of FIG. 1A.

In 380, an overcoat layer containing a photo agent material (ormaterials), such as overcoat layer 16 of FIG. 1A, is applied over thepatterned radiation-sensitive material coating. In 390, alocation-specific dose exposure process (or processes) is performed toexpose the overcoat layer and first developed radiation-sensitivematerial coating to a second wavelength (λ) of light to create localizedconcentrations of acid molecules in the overcoat layer. In 400, a secondpost-exposure bake (PEB #2) is performed to drive acid diffusion fromthe overcoat layer into the radiation-sensitive material coating andultimately de-protection of the protected polymer by the new acidincorporated into the radiation-sensitive material coating. Thelocation-specific dose exposure process and PEB#2 may include, forexample, any of the Sub Flows A-D described above, which include apost-exposure flood bake. Prior to the location-specific dose exposureprocess (at 390), and after the 1^(ST) DEV (at 360), an after-developinspection (ADI) may optionally be performed, at 370, as part of afeed-forward (FF) control strategy. Specifically, the process parametersof the location-specific dose exposure in 390, such as the dose ofelectromagnetic radiation applied to different regions of the substrate,can be altered based on a metrology data obtained from inspecting thefirst-developed radiation-sensitive material coating, as indicated bythe FF arrow.

After the location-specific dose exposure and PEB #2 processes, a seconddevelopment process (2^(ND) DEV) is performed at 410 to remove theovercoat layer and reduce the critical dimension of the patternedradiation-sensitive material coating from a first critical dimension(CD1) to a second critical dimension (CD2). In one embodiment, theovercoating, location-specific dose exposure and PEB #2 at 380 to 410are performed within the same photolithography track tool in which thepatterned layer was formed at 330 to 360. In another embodiment, theovercoating, location-specific dose exposure and PEB #2 at 380 to 410are performed in a tool separate from the photolithography track tool inwhich the patterned layer was formed at 330 to 360. At 430, theunderlying thin film is etched using the patterned radiation-sensitivematerial coating with CD2 as a mask. At 450, processing of the wafercontinues with a Next Process. A new wafer may then be processedaccording to the flow chart 300, which may be referred to as asubsequently-processed substrate.

Optionally, flow chart 300 may include ADI at 420 and/or an after-etchinspection (AEI) at 440, in which the wafer is inspected after the2^(ND) DEV at 410 and/or after the etch at 430, respectively, as part ofa feed-back (FB) control strategy. Specifically, the process parameters,e.g., dose of electromagnetic radiation applied to different regions ofthe substrate, of the location-specific dose exposure in 390 can bealtered for a subsequently processed substrate based on metrology dataobtained from inspecting the second-developed radiation-sensitivematerial coating and/or the etched underlying thin film layer, asindicated by the FB arrows. Additionally, metrology data from ADI in 370or 420 can be fed forward to the etch process in 430.

CD uniformity can vary across a surface of a substrate (i.e., wafer).For example, a given wafer can have one CD value in a center portion ofthe wafer, while having another CD value closer to an edge of a wafer. Awafer can also have CDs that vary based on order of exposureprogression, such as when using a stepper exposure system. Depending onthe particular area of a given wafer, CDs may be too large or too small,and the CD variation may be spread randomly across the wafer, may bebased on radial location, and/or may correlate with particular featuressuch as location of scribe lanes. With the prior art wet processingmethods (hot develop and/or acid rinse), this made altering WIW CDalteration amount to account for photolithography cell systematics(errors, issues) and/or external processing systematics (e.g., etch)difficult, because it would require some type of WIW concentration orrefresh rate chemical control scheme and/or high spatial resolution(zone) bake, and there was no within-die correction possible.Location-specific dose exposure hardware and control can more easilymanipulate WIW CD alteration amount process control due to being able toapply localized differences in exposure dose on the wafer (which leadsto localized differences in acid generation (loadings) in the overcoatmaterial, which ultimately facilitates localized differences in CDchanges after DEV #2). Depending on the location-specific dose exposurehardware (or hardware combinations thereof), the CD signature/systematicwithin-exposure shot/die (WIS) can be corrected as well as WIWsystematics (for instance, radial systematics, which is a WIW CDsystematic that is highly correlated with radius position, or tiltsystematics, which is a WIW CD systematic that is highly correlated witha single axis when tilt orientation is known). There are many pathwaysto feed forward WIS control. Two such correction schemes (but notlimited to) include applying an averaged field signature of all dies onthe wafer (or series of wafers, or any subset thereof) or by using adie-by-die specific correction strategy. Likewise, there are manypathways to feed forward WIW radial or tilt control. Two such methodsfor WIW radial control are 1) representing the CD wafer map by theradial terms within a multi-degree (radial/azimuthal) Zernike polynomialfit, or 2) fitting a high order polynomial to the averaged CD responsethrough radius. Two such methods for WIW tilt control are 1)representing the CD wafer map by the 1^(st) degree radial terms within aZernike polynomial fit, or 2) by finding the optimal angle at whichaveraging along the axes that is perpendicular to axes of interest, bestrepresents experimental dataset.

With regard to process control schemes, there are several FF or FBcontrol schemes that can be used independently or in conjunction withone another, as discussed above with reference to flow chart 400.Averaged after-etch inspection results can be fed back to facilitatelot-level average power setting and/or WIW power signature adjustmentsto correct for fluctuations observed with AEI. The source offluctuations can be inherent to the etch process, lithography process,and other processing steps. Likewise, averaged after-develop inspection(ADI) results can be fed back to facilitate lot-level average powersetting and/or WIW power signature adjustments to correct forfluctuations observed with ADI. In the case of CD alteration processeshaving at least 2 development steps (e.g., 360 and 410), ADI results canbe used from either ADI step (e.g., 370 or 420) and be fed back forcontrol of subsequently processed wafers. Specific to doing an ADI steppost 1^(ST) DEV (e.g., 360), but prior to CD alteration processes (e.g.,location-specific dose exposure at 390, bake at 400, 2^(ND) DEV at 410),feed forward control strategies at the wafer level are enabled. A knownADI CD map can be fed forward into a flood exposure controller toaugment the flood process (dose delivered locally within-wafer) specificto that wafer for tighter final altered CD distribution. Any of theabove control schemes used by themselves, or in conjunction, lead totighter altered CD or patterning CD control.

In sum, the aforementioned offers an alternative way to maximize the CDalteration amount achievable (break from de-protection matrix dictatedby primary exposure conditions) and to allow for more standarddevelopment conditions. It shifts CD alteration amount control to belargely controlled by flood dose versus development concentration and/ordevelop time which simplifies the CD alteration development process. Itintroduces new photo-active chemistries to be used as a primarymechanism for acid generation for CD alteration that will ultimatelylead to better de-protection control of features. Finally, it useslocation-specific critical dimension (CD) alteration/correction flowsand processes for improvement of CD uniformity, and in some embodimentsshifting of CD targeting as well, making use, in some embodiments, ofafter develop inspection (ADI) information in a feed forward (FF)process control scheme by means of localized dose control of a floodprocess step.

With this modified approach to CD alteration, WIW control schemes canalso be more realizable; allowing for tighter CD alteration orpatterning CD control.

According to an embodiment, a system is also provided for reducing thecritical dimension of a pattern formed on a substrate. The systemcomprises an overcoat spin-cup for depositing an overcoat layer atop apatterned layer on the substrate, and an exposure system for exposingthe overcoat layer to electromagnetic radiation, as discussed in detailabove. The system further includes a heating module for heating (baking)the substrate, and a developer spin-cup for applying developer to theovercoat layer and a patterned layer to reduce the critical dimension ofthe patterned layer. Additionally, the system includes a controller forcontrolling the overcoat spin cup, the exposure system, the heatingmodule, and the developer spin-cup. The controller is configured to varythe dose of electromagnetic radiation applied to different regions ofthe overcoat layer on the substrate, as discussed above, based on firstmetrology data received from a first ADI performed prior to receivingthe substrate by the system, or on second metrology data received from asecond ADI performed after an alteration of critical dimension withinthe system, or on third metrology data received from an AEI performedafter an etch process using the patterned layer as a pattern, or acombination or two or more thereof.

Various techniques have been described as multiple discrete operationsto assist in understanding the various embodiments. The order ofdescription should not be construed as to imply that these operationsare necessarily order dependent. Indeed, these operations need not beperformed in the order of presentation. Operations described may beperformed in a different order than the described embodiment. Variousadditional operations may be performed and/or described operations maybe omitted in additional embodiments.

“Substrate” as used herein generically refers to the object beingprocessed in accordance with the invention. The substrate may includeany material portion or structure of a device, particularly asemiconductor or other electronics device, and may, for example, be abase substrate structure, such as a semiconductor wafer, or a layer onor overlying a base substrate structure such as a thin film. Thus,substrate is not limited to any particular base structure, underlyinglayer or overlying layer, patterned or un-patterned, but rather, iscontemplated to include any such layer or base structure, and anycombination of layers and/or base structures. The description mayreference particular types of substrates, but this is for illustrativepurposes only.

While the present invention has been illustrated by the description ofone or more embodiments thereof, and while the embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus and methodand illustrative examples shown and described. Accordingly, departuresmay be made from such details without departing from the scope of thegeneral inventive concept.

What is claimed is:
 1. A method for patterning a substrate, comprising:receiving a substrate, the substrate comprising: an underlying layer,and a patterned layer formed on the underlying layer, the patternedlayer comprising radiation-sensitive material and further comprising apattern of varying elevation and having a first critical dimension;applying an overcoat layer over the patterned layer, the overcoat layercomprising a photo agent selected from a photosensitizer generatorcompound, a photosensitizer compound, a photoacid generator compound, aphotoactive agent, an acid-containing compound, or a combination of twoor more thereof; exposing the overcoat layer to electromagneticradiation, wherein the dose of electromagnetic radiation applied todifferent regions of the substrate is varied; heating the overcoat layerand patterned layer; and developing the overcoat layer and the patternedlayer to alter the first critical dimension of the patterned layer to asecond critical dimension.
 2. The method of claim 1, wherein the step ofexposing the overcoat layer comprises exposing the overcoat layer toultraviolet (UV) radiation.
 3. The method of claim 2, wherein thewavelength of ultraviolet (UV) radiation is from 175 nm to 450 nm. 4.The method of claim 1, wherein the step of exposing the overcoat layercomprises scanning the substrate, scanning a radiation source, rotatingthe substrate, or a combination of two or more thereof.
 5. The method ofclaim 1, wherein the step of exposing the overcoat layer comprisesexposing the overcoat layer to a scanning laser beam.
 6. The method ofclaim 1, wherein the step of exposing the overcoat layer comprisesexposing the overcoat layer to electromagnetic radiation from a digitallight projection (DLP) system.
 7. The method of claim 1, furthercomprising: receiving first metrology data from a first after-developinspection (ADI) performed prior to the step of receiving the substrate.8. The method of claim 7, further comprising: altering the dose ofelectromagnetic radiation applied to different regions of the substrateduring the step of exposing the overcoat layer based on the receivedfirst metrology data.
 9. The method of claim 1, further comprising:measuring second metrology data in a second after-develop inspection(ADI) performed after the step of developing the overcoat layer and thepatterned layer.
 10. The method of claim 9, further comprising: alteringthe dose of electromagnetic radiation applied to different regions of asubsequently-processed substrate during the step of exposing theovercoat layer based on the second metrology data.
 11. The method ofclaim 1, further comprising: etching the underlying layer using thepatterned layer having the second critical dimension as a pattern; andmeasuring third metrology data in an after-etch inspection (AEI)performed after the step of etching the underlying layer.
 12. The methodof claim 11, further comprising: altering the dose of electromagneticradiation applied to different regions of a subsequently-processedsubstrate during the step of exposing the overcoat layer based on thethird metrology data.
 13. The method of claim 1, wherein the steps ofapplying and exposing the overcoat layer, and heating and developing theovercoat layer and the patterned layer are performed within the samephotolithography track tool in which the patterned layer was formed. 14.The method of claim 1, wherein the steps of applying and exposing theovercoat layer, and heating and developing the overcoat layer and thepatterned layer are performed in a tool separate from thephotolithography track tool in which the patterned layer was formed. 15.A method, comprising: receiving a substrate, the substrate comprising:an underlying layer, and a radiation-sensitive material layer depositedon the underlying layer; exposing a first wavelength of light through apatterned mask onto the radiation-sensitive material layer andperforming a post-exposure bake; first developing the pattern-exposedradiation-sensitive material layer to form a patterned layer of varyingelevation and having a first critical dimension; inspecting thepatterned layer following the first developing; applying an overcoatlayer over the patterned layer, the overcoat layer comprising a photoagent selected from a photosensitizer generator compound, aphotosensitizer compound, a photoacid generator compound, a photoactiveagent, an acid-containing compound, or a combination of two or morethereof; exposing the overcoat layer to electromagnetic radiation at awavelength of 175 nm to 450 nm, wherein the dose of electromagneticradiation applied to different regions of the substrate is varied and isbased on metrology data obtained from inspecting the patterned layerfollowing the first developing; performing a post-exposure bake of theovercoat layer and patterned layer; and developing the overcoat layerand the patterned layer, to alter the first critical dimension of thepatterned layer to a second critical dimension.
 16. The method of claim15, wherein the step of exposing the overcoat layer comprises scanningthe substrate, scanning a radiation source, rotating the substrate, or acombination of two or more thereof.
 17. The method of claim 15, whereinthe step of exposing the overcoat layer comprises exposing the overcoatlayer to a scanning laser beam.
 18. The method of claim 15, wherein thestep of exposing the overcoat layer comprises exposing the overcoatlayer to electromagnetic radiation from a digital light projection (DLP)system.
 19. The method of claim 15, further comprising: etching theunderlying layer using the patterned layer having the second criticaldimension as a pattern.
 20. A system for reducing a critical dimensionof a pattern formed on a substrate, comprising: an overcoat spin-cup fordepositing an overcoat layer atop a patterned layer on the substrate; anexposure system for exposing the overcoat layer to electromagneticradiation; a heating module for heating the substrate; a developerspin-cup for applying developer to the overcoat layer and a patternedlayer, to reduce the critical dimension of the patterned layer, and acontroller for controlling the overcoat spin cup, the exposure system,the heating module, and the developer spin-cup, the controllerconfigured to vary the dose of electromagnetic radiation applied todifferent regions of the overcoat layer on the substrate based on firstmetrology data received from a first after-develop inspection (ADI)performed prior to receiving the substrate by the system, or on secondmetrology data received from a second after-develop inspection (ADI)performed after an alteration of critical dimension within the system,or on third metrology data received from an after-etch inspection (AEI)performed after an etch process using the patterned layer as a pattern,or a combination or two or more thereof.